How can we get this kid to stop calling at work?

I work at an electronics retailer and I answer the phones. For the last 6 months a mentally handicapped kid has been calling at least once a day. He usually is asking for tech support or he has an issue with a TV he bought, but instead of letting us help him he argues or interrupts constantly and he stays on the phone for upwards of an hour if you don’t hang up on him. He always asks for one of our other operators when he doesn’t get him on the phone. I’m not the only one receiving his calls.
Today he called and got a hold of me 5 times about his TV. I tried to help him for about 20 min. but he wasn’t listening to me and he was starting to yell. I then transferred him back to the TV department. He called back and said that they put him on hold and “forgot” about him. I transferred him again and again but he would call back. I asked my manager what I should do and she said that there was nothing we could do. Another employee took the call and was on the phone for about 2 hours.
We only have one employee answering the phones and directing the calls to the correct department or answering questions at a time so we aren’t able to stay on the phone for that long. Everyone is out of ideas. We have tried answering all of his questions, using one word answers, hanging up, putting him on hold forever. Nothing works.
I feel bad, and I want to help him, but it seems like he just wants someone to talk to and we get in trouble if too many calls go unanswered. We can’t be just outright rude, but we do need some kind of solution to get him to stop calling us.
Thanks.